The Parallel Fin Thermal Interface has been developed as an Orbital Replaceable Unit (ORU) interface. The interface transfers heat from an ORU baseplate to a Heat Acquisition Plate (HAP) through pairs of fins sandwiched between insert plates that press against the fins with uniform pressure. The insert plates are spread apart for ORU baseplate separation and replacement.Two prototype interfaces with different fin dimensions were built (Model 140 and 380). Interfacing surface samples were found to have roughnesses of 56 to 89 nm (22 to 35 μ-in.). Conductance values of 267 to 420 W/m2-°C (47 to 74 Btu/hr-ft2-°F) were obtained for the 140 model in vacuum with interface pressures of 131 to 262 kPa (19 to 38 psi). Vacuum conductances ranging from 176 to 267 W/m2-°F (31 to 47 Btu/hr-ft2-°F) were obtained for the 380 model at interface pressures of 97 to 152 kPa (14 and 22 psi). Correlations from several sources were found to agree with test data within 20% using Thermal Math Models of the interfaces.